Fill a wireframe with a material?
I guess you are using the Wireframe modifier. Instead use the Wireframe input Node to affect a Mix Shader Node

Here we have a Diffuse BSDF Node (Red) and a Transparent Shader mixed together. Without a Factor they will blend together to a pale Red.
With the Wireframe input as the factor only where the wireframe exists is Red, everywhere else is 100% transparent


As the geometry is not affected another material on the smae or duplicate object can be just solid.